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Chapter 5
Applying Cisco's Diagnostic Tools
What are your observations? Check your list with the following:
No IP address is configured on Ethernet 0/0.
Output packets generated on Ethernet 0/0 with the same number of
output errors.
The same number of lost carrier errors as the number of output errors.
Serial 0/0 is administratively shut down.
Ethernet 0/1 is up and up.
This list can contain more information regarding the interfaces, such as
encapsulation types and so on. For clarity and simplicity, only the observa-
tions that are relevant to this scenario are listed.
After observations and fact-gathering are completed, it is time to formu-
late a problem description. Initially, from what you saw while the router
booted, the problem description was vague. It could have been written some-
thing like this: "Interfaces Ethernet 0/0 and Serial 0/0 are down."
This is a good start, but it lacks detail. If this were a complicated problem,
you could be troubleshooting for a long time because the description lacks
focus.
Based on listed observations, you know exactly what the problem descrip-
tion is. Here is a sample of a focused and detailed problem statement or
description: "Ethernet 0/0 is down because it doesn't have a carrier, and
Serial 0/0 is down because it was administratively shut down."
With this problem statement, it should be obvious what needs to be done
to fix the problems.
Propose Solutions
How did you do? Now that you observed these problems, what are the solu-
tions? This relates to the "creating an action plan" part of the troubleshoot-
ing method. The more specific the problem statement, the more easily the
solutions can be defined.
In the first scenario, there appear to be a few problems that need resolu-
tion. They are all simple solutions in this case:
Check the cable and transceiver for the Ethernet port for a possible
physical problem with the interface.
Configure an IP address on Ethernet 0/0
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